Receiver for receiving radio frequency signals

ABSTRACT

Receivers ( 1 ) for receiving radio frequency signals need automatic gain control alignment by hand during the production process, which makes the production process more expensive, more time-consuming and less reliable (insight). By (basic idea) providing receivers ( 1 ) with a first and a second gain controller ( 38, 54 ) for controlling the gains of a first (radio frequency) and a second (intermediate frequency) stage ( 3, 5 ) independently from each other, alignment by hand is no longer necessary, which results in a less expensive, less time-consuming and more reliable production process. The gain controllers ( 38, 54 ) have gain detectors ( 41, 59 ) for detecting output signals, and gain generators ( 40, 58 ) for generating gain control signals, and control inputs ( 42, 60 ) for receiving the same reference level signal (REF) for controlling the gains in relation to the same reference level.

The invention relates to a receiver for receiving radio frequencysignals, and also relates to a tuner, a demodulator, a processor, amethod and a processor program product.

Such a receiver for example corresponds with a television receivercomprising two or more receiver stages, a first radio frequency stagefor example forming part of and/or corresponding with a tuner, and asecond intermediate frequency stage for example forming part of and/orcorresponding with a demodulator.

A prior art receiver is known from EP 0 961 492 A2, which discloses atuner for receiving an analog television signal and a digital televisionsignal. To be able to tune and demodulate both kinds of signals, twodemodulator-detector-combinations are provided, whereby one of thecombinations is switched and coupled to the tuner in dependence of thekind of signals arriving. For getting an automatic gain control, thedetector is fed back to an amplifier in the tuner via a voltageconverting circuit.

The known receiver is disadvantageous, inter alia, due to requiringautomatic gain control alignment of the tuner during the productionprocess. This alignment is done by hand, which makes the productionprocess more expensive, more time-consuming and less reliable.

It is an object of the invention, inter alia, of providing a receiverthat does not require alignment by hand during the production process.The invention is defined by the independent claims. The dependent claimsdefine advantageous embodiments.

Further objects of the invention are, inter alia, providing a tuner, ademodulator and a processor for use in a receiver that does not requirealignment by hand during the production process, and a method and acomputer program product for receiving radio frequency signals withoutrequiring alignment by hand.

By providing the receiver with two or more gain controllers forcontrolling the gains of the two or more stages independently from eachother, alignment by hand is no longer necessary. As a result, theproduction process will be less expensive, less time-consuming and morereliable. Further, calibration, replacement and repairing costs areavoided, and an improved signal-to-noise ratio will be achievedindependently of circuit deviations and for the entire life of thereceiver, not just during the production process.

It should be noted that it is known to use two gain controllers forcontrolling the gains of the two stages. However, these two gaincontrollers do not control the gains independently from each other, thesecond gain controller in this prior art case also controls the firstgain controller. Under these prior art circumstances, alignment by handduring the production process is still necessary.

A first embodiment of the receiver according to the invention is definedby claim 2. By adjusting both gain controllers at the same referencelevel for controlling the gains in relation to this reference level,both stages are gain controlled in relation to the same reference level.As a result, both stages are coupled optimally (and a further improvedsignal-to-noise ratio will be achieved). This reference level is chosenduring the designing process and in dependence of the design.

A second embodiment of the receiver according to the invention isdefined by claim 3. By providing the first gain controller with a firstgain detector for detecting an output signal of one or more firstintermediate frequency amplifiers in the second stage and with a firstgain generator for generating, in response to the detecting, a firstgain control signal to be supplied to a control input of a radiofrequency amplifier in the first stage, a simple first gain controllerhas been created which controls the gain of the first stage including afilter (like for example a SAW filter) located between the first stageand the second stage.

A third embodiment of the receiver according to the invention is definedby claim 4. By providing the second gain controller with a second gaindetector for detecting an output signal of one or more intermediatefrequency demodulator stages and with a second gain generator forgenerating, in response to the detecting, a second gain control signalto be supplied to a control input of one or more second intermediatefrequency amplifiers in the second stage, a simple second gaincontroller has been created.

Each one of the gain controllers may for example comprise ananalog-to-digital converter, a processor with one or more memories likefor example table memories, and a digital-to-analog converter asdisclosed in U.S. Pat. No. 5,194,822. Or, each one of the gaincontrollers may have a kind of Phase Locked Loop or Feedback Loopconstruction.

Embodiments of the tuner according to the invention and of thedemodulator according to the invention and of the processor according tothe invention and of the method according to the invention and of theprocessor program product according to the invention correspond with theembodiments of the receiver according to the invention.

The invention is based upon an insight, inter alia, that alignment byhand makes the production process expensive, more time-consuming andless reliable, and is based upon a basic idea, inter alia, that two ormore gain controllers for controlling the gains of two or more stagesindependently from each other can replace this aligning.

The invention solves the problem, inter alia, of providing a receiverthat does not require alignment by hand during the production process,and is advantageous, inter alia, in that the production process will beless expensive, less time-consuming and more reliable. Further,calibration, replacement and repairing costs are avoided, and animproved signal-to-noise ratio will be achieved independently of circuitdeviations and for the entire life of the receiver, not just during theproduction process.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments(s) described hereinafter.

FIG. 1 shows diagrammatically a receiver according to the inventioncomprising a first stage and a second stage,

FIG. 2 shows diagrammatically a first stage with a first gaincontroller, and

FIG. 3 shows diagrammatically a second stage with a second gaincontroller.

The receiver 1 according to the invention shown in FIG. 1 comprises afirst (radio frequency) stage 3 having a radio frequency input 2 coupledto an antenna for receiving a radio frequency signal like a variety ofmodulated carriers and having an intermediate frequency output 6 coupledto an input of a SAW filter 4. An output of SAW filter 4 is coupled toan input 7 of a second (intermediate frequency) stage 5 having a videooutput 12 for generating a video signal. First stage 3 further comprisesa control input 8 coupled to a control output 9 of second stage 5.

First stage 3 shown in FIG. 2 comprises a filter 30 of which an input iscoupled to input 2 and of which an output is coupled to an input of aradio frequency amplifier 31. An output of radio frequency amplifier 31is coupled to an input of a filter 32, of which an output is coupled toa first input of a mixer 33. An output of mixer 33 is coupled to aninput of a filter 34, of which an output is coupled to an input of afurther amplifier 35. An output of further amplifier 35 is coupled tooutput 6. First stage 3 further comprises a Phase Locked Loop 36(possibly including a crystal clock) of which an output is coupled to aninput of an oscillator 37. A first output of oscillator 37 is coupled toa second input of mixer 33, and a second output of oscillator 37 iscoupled to control inputs of filters 30 and 32. An input of a first gaincontroller 38 comprising a first gain detector 41 and a first gaingenerator 40 is coupled to control input 8, and a control input 42 offirst gain controller 38 receives a reference level signal REF, and anoutput of first gain controller 38 is coupled to a control input 39 ofradio frequency amplifier 31 for varying an amplification factor ofradio frequency amplifier 31.

Second stage 5 shown in FIG. 3 comprises one or more first intermediatefrequency amplifiers 50 of which an input is coupled to input 7 and ofwhich an output is coupled to an input of one or more secondintermediate frequency amplifiers 51 and to control output 9. An outputof second intermediate frequency amplifier 51 is coupled to a firstinput of an intermediate frequency demodulator stage 52, of which anoutput is coupled to an input of a video amplifier 53 and to an input ofa second gain controller 54 comprising a second gain detector 59 and asecond gain generator 58. An output of video amplifier 53 is coupled tovideo output 12, and an output of second gain controller 54 is coupledto a control input 57 of second intermediate frequency amplifier 51 forvarying an amplification factor of second intermediate frequencyamplifier 51, and a control input 60 of second gain controller 54receives the reference level signal REF. Second stage 5 furthercomprises a Phase Locked Loop 55 of which a first input is coupled to anoutput of second intermediate frequency amplifier 51 and of which asecond input is coupled to an output of an oscillator 56 and of which anoutput is coupled to an input of oscillator 56. The output of oscillator56 is further coupled to a second input of intermediate frequencydemodulator stage 52.

The receiver 1 according to the invention functions as follows. Supposefrom the antenna at radio frequency input 2 a radio frequency signal isreceived at 100 dBuV. In case of the first stage 3 having a gain of 50dB and the SAW filter 4 loss being 20 dB, without the first gaincontroller 38 being active, the intermediate frequency signal suppliedto first intermediate frequency amplifier 50 will be at 130 dBuV and incase of this first intermediate frequency amplifier 50 having a gain of5 dB (the gain of first intermediate frequency amplifier 50 is chosenlow to be more accurate, higher gains would show larger deviations), theintermediate frequency signal at the output of first intermediatefrequency amplifier 50 will be at 135 dBuV. First gain controller 38compares the 135 dBuV with the reference level set by the (intermediate)reference level signal REF, for example 100 dBuV. The difference between135 dBuV and 100 dBuV results in a first gain control signal beingsupplied to control input 39 of radio frequency amplifier 31 in thefirst stage 3. In response to this first gain control signal, theamplification factor of radio frequency amplifier 31 is varied such thatthe first stage 3 gets a gain of 20 dB (30 dB reduction). Then theintermediate frequency signal supplied to first intermediate frequencyamplifier 50 will be at 105 dBuV and in case of this first intermediatefrequency amplifier 50 having a gain of 5 dB, the intermediate frequencysignal at the output of first intermediate frequency amplifier 50 willbe at 100 dBuV, which is the reference level set by the (intermediate)reference level signal REF.

In second stage 5, second intermediate frequency amplifier 51 forexample comprises two amplifiers with gains of 25 dB and 35 dB. Secondgain controller 54 compares the output signal of intermediate frequencydemodulator stage 52 with a standard level, for example 2 Vpp or 1 Vppetc. The difference between the output signal and this standard levelresults in a second gain control signal being supplied to control input57 of second intermediate frequency amplifier 51 in the second stage 5.In response to this second gain control signal, the amplification factorof second intermediate frequency amplifier 51 (of one or of bothamplifiers) is varied such that the second stage 5 gets a gain such thatthe output signal of intermediate frequency demodulator stage 52 is atthe standard level. Alternatively, the output signal of secondintermediate frequency amplifier 51 may be detected by second gaincontroller 54. Generally, the reference level set by the (intermediate)reference level signal REF defines a desired output level of the firstintermediate frequency amplifier 50. The (intermediate) reference levelsignal REF supplied to second gain controller 54 limits the gainreduction at the second intermediate frequency amplifier 51. The maximumgain reduction at the second intermediate frequency amplifier 51 is forexample equal to the reference level set by the (intermediate) referencelevel signal REF plus the gain of first and second intermediatefrequency amplifiers 50 and 51 minus the standard level of the outputsignal of intermediate frequency demodulator stage 52; other functionsand/or equations are not to be excluded. The maximum gain reductionlimitation is required to avoid an excessive gain reduction in thesecond intermediate frequency amplifier 51 that leads to a deterioratedsignal-to-noise ration.

As a result of letting gain controllers 38 and 54 control the gains ofthe first and the second stage 3 and 5 independently from each other,automatic gain control alignment during the production process can beavoided advantageously.

Second gain controller 54 for example comprises an analog-to-digitalconverter, a processor with one or more memories like for example tablememories, and a digital-to-analog converter. Then, second gain detector59 comprises the analog-to-digital converter and a part of the processorand the memories, and the second gain generator 58 comprises the otherpart of the processor and the memories and the digital-to-analogconverter. In the case, control input 60 for example forms a controlinput of second gain detector 59 for receiving the reference levelsignal REF (like for example 100 dBuV or AGC DAC step 10). For examplethe following table is thereby implemented (AGC DAC=Automatic GainControl Digital to Analog Converter).

AGC DAC step Reference level signal REF (in dBuV) 00 110 01 109 02 108 .. . . . . 18 92 19 91 20 90First gain controller 38 for example comprises an analog-to-digitalconverter, a processor with one or more memories like for example tablememories, and a digital-to-analog converter. Then, first gain detector41 comprises the analog-to-digital converter and a part of the processorand the memories, and the second gain generator 40 comprises the otherpart of the processor and the memories and the digital-to-analogconverter. In that case, control input 42 for example forms a controlinput of first gain detector 41 for receiving the reference level signalREF (like for example 100 dBuV or AGC DAC step 10). As a result ofsupplying the same reference level signal REF to second gain controller54 and to first gain controller 38, both stages 3 and 5 are gaincontrolled in relation to the same reference level, and are thereforecoupled optimally. This reference level is chosen during the designingprocess and in dependence of the design.

Alternatively, each one of the gain controllers 38,54 may have a kind ofPhase Locked Loop or Feedback Loop construction. First gain controller38 may form part of first stage 3 or not, and/or may be integrated intoradio frequency amplifier 31 or not, and/or may be integrated into firstintermediate frequency amplifier 50 or not. Second gain controller 54may form part of second stage 5 or not, and/or may be integrated intosecond intermediate frequency amplifier 51 or not, etc.

The expression “for” in for example “for A” and “for B” does not excludethat other functions “for C” are performed as well, simultaneously ornot. The expressions “X coupled to Y” and “a coupling between X and Y”and “coupling/couples X and Y” etc. do not exclude that an element Z isin between X and Y. The expressions “P comprises Q” and “P comprising Q”etc. do not exclude that an element R is comprised/included as well.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall not be construed as limiting the claim.Use of the verb “comprise” and its conjugations does not exclude thepresence of elements or steps other than those stated in a claim. Thearticle “a” or “an” preceding an element does not exclude the presenceof a plurality of such elements. The invention may be implemented bymeans of hardware comprising several distinct elements, and by means ofa suitably programmed computer. In the device claim enumerating severalmeans, several of these means may be embodied by one and the same itemof hardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

1. A receiver for receiving radio frequency signals and comprising: afirst stage for amplifying and tuning radio frequency signals and forgenerating intermediate frequency signals; a first gain controller forcontrolling a gain of the first stage; a second stage for amplifying anddemodulating the intermediate frequency signals; and a second gaincontroller for controlling a gain of the second stage; which first andsecond gain controllers control the gains independently from each otherwith the first gain controller to control the gain of the first stagebased on a modulated intermediate frequency signal at an input of thefirst gain controller, and the second gain controller to control thegain of the second stage based on a demodulated intermediate frequencysignal at an input of the second gain controller, wherein both gaincontrollers are adjusted at the same reference level for controlling thegains in relation to this reference level.
 2. A receiver according toclaim 1, wherein the second stage comprises a first intermediatefrequency amplifier and a second intermediate frequency amplifier, withthe first gain controller comprising a first gain detector for detectingan output signal of the first intermediate frequency amplifier and afirst gain generator for generating, in response to the detecting, afirst gain control signal to be supplied to a control input of a radiofrequency amplifier in the first stage.
 3. A receiver according to claim2, wherein the second stage comprises an intermediate frequencydemodulator stage having an input coupled to an output of the secondintermediate frequency amplifier and an output coupled to an input of avideo amplifier for generating a video signal, with the second gaincontroller comprising a second gain detector for detecting an outputsignal of the intermediate frequency demodulator stage and a second gaingenerator for generating, in response to the detecting, a second gaincontrol signal to be supplied to a control input of the secondintermediate frequency amplifier.
 4. A tuner for use in a receiver forreceiving radio frequency signals, which receiver comprises a firststage for amplifying and tuning radio frequency signals and forgenerating intermediate frequency signals; a first gain controller forcontrolling a gain of the first stage; a second stage for amplifying anddemodulating the intermediate frequency signals; a second gaincontroller for controlling a gain of the second stage; which first andsecond gain controllers control the gains independently from each otherwith the first gain controller to control the gain of the first stagebased on a modulated intermediate frequency signal at an input of thefirst gain controller, and the second gain controller to control thegain of the second stage based on a demodulated intermediate frequencysignal at an input of the second gain controller, and which tunercomprises the first stage and the first gain controller, wherein bothgain controllers are adjusted at the same reference level forcontrolling the gains in relation to this reference level.
 5. A tuneraccording to claim 4, wherein the second stage comprises a firstintermediate frequency amplifier and a second intermediate frequencyamplifier, with the first gain controller comprising a first gaindetector for detecting an output signal of the first intermediatefrequency amplifier and a first gain generator for generating, inresponse to the detecting, a first gain control signal to be supplied toa control input of a radio frequency amplifier in the first stage.
 6. Atuner according to claim 5, wherein the second stage comprises anintermediate frequency demodulator stage having an input coupled to anoutput of the second intermediate frequency amplifier and an outputcoupled to an input of a video amplifier for generating a video signal,with the second gain controller comprising a second gain detector fordetecting an output signal of the intermediate frequency demodulatorstage and a second gain generator for generating, in response to thedetecting, a second gain control signal to be supplied to a controlinput of the second intermediate frequency amplifier.
 7. A demodulatorfor use in a receiver for receiving radio frequency signals, whichreceiver comprises: a first stage for amplifying and tuning radiofrequency signals and for generating intermediate frequency signals; afirst gain controller for controlling a: gain of the first stage; asecond stage for amplifying and demodulating the intermediate frequencysignals; and a second gain controller for controlling a gain of thesecond stage; which first and second gain controllers control the gainsindependently from each other with the first gain controller to controlthe gain of the first stage based on a modulated intermediate frequencysignal at an input of the first gain controller, and the second gaincontroller to control the gain of the second stage based on ademodulated intermediate frequency signal at an input of the second gaincontroller, and which demodulator comprises the second stage and thesecond gain controller, wherein both gain controllers are adjusted atthe same reference level for controlling the gains in relation to thisreference level.
 8. A demodulator according to claim 7, wherein thesecond stage comprises a first intermediate frequency amplifier and asecond intermediate frequency amplifier, with the first gain controllercomprising a first gain detector for detecting an output signal of thefirst intermediate frequency amplifier and a first gain generator forgenerating, in response to the detecting, a first gain control signal tobe supplied to a control input of a radio frequency amplifier in thefirst stage.
 9. A demodulator according to claim 8, wherein the secondstage comprises an intermediate frequency demodulator stage having aninput coupled to an output of the second intermediate frequencyamplifier and an output coupled to an input of a video amplifier forgenerating a video signal, with the second gain controller comprising asecond gain detector for detecting an output signal of the intermediatefrequency demodulator stage and a second gain generator for generating,in response to the detecting, a second gain control signal to besupplied to a control input of the second intermediate frequencyamplifier.
 10. A method for receiving radio frequency signals andcomprising: a first step of amplifying and tuning radio frequencysignals and of generating intermediate frequency signals; a second stepof controlling a gain of the first step; a third step of amplifying anddemodulating intermediate frequency signals; a fourth step ofcontrolling a gain of the third step; which second and fourth stepscontrol the gains independently from each other, wherein one of thecontrol inputs for the gain controllers is taken from a modulated IFsignal at an input of a first gain controller, and one of the controlinputs for the gain controllers is taken from a demodulated IF signal atan input of a second gain controller, and adjusting the gain of thefirst and third steps at the same reference level for controlling thegains in relation to this reference level.
 11. A method according toclaim 10, wherein controlling the gain of the first step furthercomprises: detecting in a first stage an output signal of a firstintermediate frequency amplifier in a second stage; and generating, inresponse to the detecting, a first gain control signal for controllingthe gain of the first step.
 12. A method according to claim 11, whereincontrolling the gain of the second step further comprises: detecting inthe second stage an output signal of an intermediate frequencydemodulator stage; and generating, in response to the detecting, asecond gain control signal for controlling the gain of the second step.